Distributed Antenna Narrowband Interference Cancellation in Uplink Paths
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Distributed antenna systems face interference from narrowband signals, which overdrive receivers and cause intermodulation distortion, leading to degraded channel performance, and existing solutions increase noise figure and desensitize receivers.
Innovation Solution
A cancellation subsystem is implemented in remote antenna units, comprising a decimator, filter, and interpolator, which generates and applies a cancellation signal to subtract narrowband interfering components from uplink signals, using a reference path parallel to the uplink path, thereby reducing distortion without increasing noise figure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gain of the receiver is reduced to handle narrowband interfering signals, then intermodulation distortion is reduced, but the noise figure increases and the receiver becomes desensitized
Solution Approach 1:
The receiver signal path is segmented into multiple processing branches: a narrowband path for interfering signals and a wideband path for desired signals. The narrowband path processes only the interfering GSM frequencies while the wideband path processes all other frequencies, allowing independent optimization of each path without mutual interference.
Solution Approach 2:
The narrowband interfering signal is extracted and removed from the wideband receiver signal. A separate narrowband receiver path is used to capture and process only the interfering GSM signals, which are then cancelled out in the wideband path, leaving the desired wideband signals intact.
2Power
If high power levels are used to transmit uplink signals to overcome path loss, then signal strength at the base station is improved, but the receiver of the remote antenna unit becomes overdriven
Solution Approach 1:
A cancellation signal acts as an intermediary to neutralize the effect of narrowband interfering signals on the receiver. The cancellation signal is generated to match the interfering signal characteristics and is subtracted from the received signal, effectively removing the harmful interference before it can cause overdrive or distortion.
Solution Approach 2:
The system performs preliminary processing to identify and cancel narrowband interfering signals before they can cause harmful effects. By detecting the presence of narrowband interferers and generating cancellation signals in advance, the system prevents receiver overdrive and intermodulation distortion before they occur.
Data Source
AI summary
Canceling narrowband interfering signals in a distributed antenna system is provided. In one aspect, a cancellation sub-system includes a decimator module, a filter, an interpolator module, and a combiner module coupled to the uplink path and a reference path in parallel with the uplink path. The reference path includes the decimator module, the filter, and the interpolator module. The decimator module decimates a reference signal sampled from an uplink signal traversing an uplink path of the remote antenna unit. Each of the uplink signal and the reference signal includes a narrowband interfering signal component. The filter generates a cancellation signal from the reference signal by attenuating the reference signal outside a frequency band that includes the interfering signal component. The interpolator module interpolates the cancellation signal to a sampling rate of the uplink signal. The combiner module can subtract the cancellation signal from the uplink signal.